I am very right hand dominant, but I play hockey as a lefty.
As for epi-whatever, Wikipedia has a very good "article" on finger length. The key premise is that finger length is correlated to a 39 month long estrogen/testosterone wash, and is not genetically determined.
I do believe that there is some generic inheritance pattern. I have a very small extended family, but on my paternal mother's side of the family, there are 4 out of 25 or so "non-binary": a gay man, a lesbian, a lesbian or possibly FtM and me, "just a CD". It seems like a very percentage of non-binary and a wide variety of non-binary expressions.